Towards reliable assessment of pyroclastic density current hazards

实现火山碎屑密度电流危害的可靠评估

基本信息

批准号：
NE/V014242/1
负责人：
Eric Breard
金额：
$ 81.26万
依托单位：
University of Edinburgh
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2022
资助国家：
英国
起止时间：
2022 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FV014242%2F1
关键词：
Towards reliable assessment pyroclastic density

项目摘要

In a world where the human population keeps growing and is pushed to living in hazardous volcanic areas, volcanoes are increasingly becoming a larger threat to life. Volcanoes that erupt explosively have had devastating societal impacts, including covering countries in ash, changing the climate, and the extensive loss of human life. The most serious class of volcanic hazards is caused by volcanic flows, which include landslides, debris flows and the most dangerous of all, pyroclastic flows. Pyroclastic flows, made of scorching ash and gas, can burn and bury entire cities within minutes. These hot currents are typically composed of a basal dense avalanche and overriding dilute turbulent ash-cloud surge. Pyroclastic flows do not solely affect the ground, as they can also form large plumes of fine ash particles that rise to the altitude of cruising flights and can disrupt aviation paths. Predicting the propagation of these flows has been one of the largest challenges in geosciences because we lack a fundamental understanding of how complex granular media flow, i.e. our understanding of their rheology is very incomplete. This gap in our knowledge makes the impacts from pyroclastic flows very difficult to predict. The ability to forecast future pyroclastic flow velocity and inundation areas would help to limit the loss of human life and reduce economic impacts by informing mitigation strategies such as evacuations. Unfortunately, this goal cannot be achieved until we capture the physics of these currents and implement it in numerical models. The dense avalanche layer is a highly complex granular flow made of particles spanning a wide range of sizes (from microns to meters). The gas-particle coupling leads to elevated gas pressure and enables the transformation of the highly frictional granular avalanche into a mixture analogous to a liquid. While our understanding of granular flows has grown significantly in the past decade, previous studies have focused on steady configurations and simplified mixtures of grains. In nature, pyroclastic flows evolve over time as particles fragment and abrade by colliding with each other, and flows propagate across a variety of topographic obstacles such as valleys that control their behaviour, making their behaviour transient. Without a physical description of unsteady rheology of natural volcanic mixtures, we may never capture their behaviour accurately. Another major challenge we face is the time that current models require to run simulations of pyroclastic flows on highly resolved digital-elevation models. At the moment, all models use Central Processing Unit (CPU) computing to simulate volcanic flows, and require supercomputers to solve hundreds of scenarios taking days to weeks to complete. This project will take advantage of recent advances in computing abilities and analytical techniques available in physics and engineering and apply these to geosciences. These techniques will be used to study the dissipation energy from unsteady pyroclastic mixtures, enabling physical descriptions of the processes to be implemented in a new generation of volcanic flow model based on graphic cards. This new model will use Graphic Processing Unit (GPU) computing that can be undertaken on any laptop. This new model will allow highly resolved calculations and will radically transform our ability to forecast pyroclastic flow hazards and their interaction with topography, and enable volcanologists to undertake rapid hazard assessment when most needed: during volcanic unrest. Combining the findings and development from this study with other fields in geosciences will lead to important advances in how volcanic hazard assessment is undertaken and help limit loss of life.

在人口不断增长并被迫生活在危险的火山地区的世界中，火山日益成为对生命的更大威胁。爆发性喷发的火山造成了毁灭性的社会影响，包括火山灰覆盖多个国家、改变气候以及造成大量人员伤亡。最严重的一类火山灾害是由火山流引起的，其中包括山体滑坡、泥石流和最危险的火山碎屑流。由灼热的灰烬和气体组成的火山碎屑流可以在几分钟内燃烧并掩埋整个城市。这些热流通常由底部密集的雪崩和压倒性的稀湍流火山灰云涌组成。火山碎屑流不仅影响地面，还可能形成大量细小火山灰颗粒，上升到巡航航班的高度，并可能扰乱航空路线。预测这些流动的传播一直是地球科学中最大的挑战之一，因为我们缺乏对复杂颗粒介质如何流动的基本了解，即我们对其流变学的理解非常不完整。我们知识上的差距使得火山碎屑流的影响很难预测。预测未来火山碎屑流速和淹没区域的能力将有助于限制人员生命损失，并通过告知疏散等缓解策略来减少经济影响。不幸的是，只有我们捕获这些电流的物理原理并在数值模型中实现它，这个目标才能实现。致密雪崩层是一种高度复杂的颗粒流，由各种尺寸（从微米到米）的颗粒组成。气体-颗粒耦合导致气体压力升高，并使高摩擦力的粒状雪崩转变为类似于液体的混合物。虽然我们对颗粒流的理解在过去十年中显着增长，但之前的研究主要集中在稳定的结构和简化的颗粒混合物上。在自然界中，火山碎屑流随着粒子相互碰撞而破碎和磨损而随着时间的推移而演变，并且流穿过各种地形障碍物（例如控制其行为的山谷）传播，从而使其行为变得短暂。如果没有对天然火山混合物的不稳定流变学的物理描述，我们可能永远无法准确地捕捉它们的行为。我们面临的另一个主要挑战是当前模型需要在高分辨率数字高程模型上运行火山碎屑流模拟所需的时间。目前，所有模型都使用中央处理器（CPU）计算来模拟火山流，并需要超级计算机来解决数百个场景，需要几天到几周的时间才能完成。该项目将利用物理和工程领域计算能力和分析技术的最新进展，并将其应用于地球科学。这些技术将用于研究不稳定火山碎屑混合物的耗散能量，从而能够在基于显卡的新一代火山流模型中实现过程的物理描述。这个新模型将使用图形处理单元（GPU）计算，可以在任何笔记本电脑上进行。这个新模型将允许进行高精度计算，并将从根本上改变我们预测火山碎屑流灾害及其与地形相互作用的能力，并使火山学家能够在最需要的时候（即火山动荡期间）进行快速灾害评估。将这项研究的发现和发展与地球科学的其他领域相结合，将在火山灾害评估的实施方式方面取得重要进展，并有助于限制生命损失。